Indoor air within and around enclosed environments, such as buildings, vehicles and structures, is affected by a plurality of contaminants. Among these contaminants, often with the highest concentration, is carbon dioxide (CO2). There are other contaminants which may appear in relatively lower concentrations yet are no less important to monitor and/or reduce. A class of such contaminants is a group of species of organic vapors, broadly referred to as Volatile Organic Compounds (VOC). Contaminant gases (e.g., CO2) and VOCs, and corresponding vapors thereof, may collectively be referred to as a “gas(es)”. The sources of these contaminants include, inter alia, the human occupants themselves—from respiration and perspiration, to clothing and cosmetics—as well as building materials, equipment, food and consumer products, cleaning materials, office supplies or any other materials which emit VOCs. Other classes of contaminants are inorganic compounds and microorganisms such as bacteria, viruses, mold, fungi and airborne particles. Additional gaseous contaminants may be sulfur oxides, nitrous oxides, radon, or carbon monoxide.
Heating, Ventilation and Air-Conditioning (“HVAC”) is used in virtually every modern building. One of the goals of HVAC systems is to provide a comfortable and healthy environment for the enclosed environment occupants, in terms of temperature, humidity, composition and quality of air.
In order to maintain good air quality, not all the air is returned. Some of the air is exhausted out of the enclosed environment and is replaced by an intake of fresh air from the outside. This is sometimes referred to as “fresh air”, “makeup air” or ventilation. Such replacement of the air dilutes the contaminants within the indoor air and helps maintain good air quality in the enclosed environment.
However, there are a number of drawbacks to fresh air ventilation, including the energy required to condition the outdoor air (i.e., heat, cool, de-humidify), as well as the potential introduction of pollutants and contaminants from the outside into the enclosed environment. One possible solution to these drawbacks is to selectively remove the contaminants from indoor air, and certain schemes have been proposed for this purpose in conjunction with HVAC systems. For example, a system for removing the contaminants from indoor air in a HVAC system is disclosed in applicant's U.S. Pat. No. 8,157,892, which is incorporated herein by reference in its entirety.
Selective contaminant removal from the HVAC system is performed by directing the return air to a contaminant remover system and thereafter introducing the now treated return air back into the enclosed environment.